Provided is a recording apparatus including a self-excited oscillation semiconductor laser that has a double quantum well separate confinement heterostructure and includes a saturable absorber section to which a negative bias voltage is applied and a gain section into which a gain current is injected, an optical separation unit, an objective lens, a light reception element, a pulse detection unit, a reference signal generation unit, a phase comparison unit, a recording signal generation unit, and a control unit.
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1. A recording apparatus comprising: a self-excited oscillation semiconductor laser that has a double quantum well separate confinement heterostructure and includes a saturable absorber section to which a negative bias voltage is applied and a gain section into which a gain current is injected; an optical separation unit that separates an oscillated light beam from the self-excited oscillation semiconductor laser into two oscillated light beams; an objective lens that condenses one of the separated oscillated light beams on an optical recording medium; a light reception element that receives the one of the oscillated light beams separated by the optical separation unit; a pulse detection unit that detects a pulse of the oscillated light beam received by the light reception element; a reference signal generation unit that generates a master clock signal; a phase comparison unit that calculates a phase difference between the master clock signal and the pulse; a recording signal generation unit that generates a recording signal using a negative voltage at a timing of the master clock signal; and a control unit that controls the negative bias voltage to be applied to the saturable absorber section based on the recording signal and that outputs a direct current voltage during a non-oscillation period of the self-excited oscillation semiconductor laser and outputs a period voltage changed at a desired period during an oscillation period of the self-excited oscillation semiconductor laser; wherein the control unit controls the gain current to be injected into the gain section of the self-excited oscillation semiconductor laser based on the phase difference and adjusts an interval of the pulse during the oscillation period.
The recording apparatus uses a special semiconductor laser. This laser, called a self-excited oscillation laser, has a double quantum well structure and is divided into two sections: a saturable absorber (gets a negative voltage) and a gain section (gets current). The laser emits a light beam that's split into two. One beam is focused by a lens onto a disc to record data. The other beam goes to a sensor that detects pulses of light. A circuit generates a steady clock signal. The system measures the difference between the clock signal and the laser pulse. A control circuit adjusts the negative voltage on the absorber based on a recording signal that's generated using the clock signal. During laser off-time, the control unit sends a fixed voltage; during laser on-time, it sends a voltage that changes at a set frequency. The control circuit also adjusts the current into the gain section based on the timing difference, changing the pulse rate.
2. The recording apparatus according to claim 1 , wherein the self-excited oscillation semiconductor laser includes an active layer, a GaInN guide layer, a p-type AlGaN barrier layer, a p-type GaN/AlGaN superlattice first-clad layer, and a p-type GaN/AlGaN superlattice second-clad layer, and the GaInN guide layer, the p-type AlGaN barrier layer, the p-type GaN/AlGaN superlattice first-clad layer, and the p-type GaN/AlGaN superlattice second-clad layer are sequentially laminated on one surface of the active layer.
The self-excited oscillation semiconductor laser from the previous recording apparatus includes several layers stacked on top of each other. On one side of an active layer are the following layers (in order): a GaInN guide layer, a p-type AlGaN barrier layer, a p-type GaN/AlGaN superlattice first-clad layer, and a p-type GaN/AlGaN superlattice second-clad layer. These layers help confine light and improve laser performance.
3. The recording apparatus according to claim 2 , wherein the self-excited oscillation semiconductor laser includes an n-type GaN guide layer, an n-type AlGaN clad layer, and an n-type GaN layer that are sequentially formed on the other surface of the active layer.
On the other side of the active layer of the self-excited oscillation semiconductor laser described in the previous recording apparatus claims are these layers (in order): an n-type GaN guide layer, an n-type AlGaN clad layer, and an n-type GaN layer. This complements the structure on the other side of the active layer, further optimizing the laser's optical properties.
4. An optical oscillation device comprising: a self-excited oscillation semiconductor laser that has a double quantum well separate confinement heterostructure and includes a saturable absorber section to which a negative bias voltage is applied and a gain section into which a gain current is injected; an optical separation unit that separates an oscillated light beam from the self-excited oscillation semiconductor laser; a light reception element that receives one of the oscillated light beams separated by the optical separation unit; a pulse detection unit that detects a pulse of the oscillated light beam received by the light reception element; a reference signal generation unit that generates a master clock signal; a phase comparison unit that calculates a phase difference between the master clock signal and the pulse; a signal generation unit that generates a predetermined signal using a negative voltage at a timing of the master clock signal; and a control unit that controls the negative bias voltage to be applied to the saturable absorber section based on the signal and that outputs a direct current voltage during a non-oscillation period of the self-excited oscillation semiconductor laser and outputs a period voltage changed at a desired period during an oscillation period of the self-excited oscillation semiconductor laser; and wherein the control unit controls the gain current to be injected into the gain section of the self-excited oscillation semiconductor laser based on the phase difference and adjusts an amplitude of the pulse within the oscillation period.
The optical oscillation device uses a special semiconductor laser. This laser, called a self-excited oscillation laser, has a double quantum well structure and is divided into two sections: a saturable absorber (gets a negative voltage) and a gain section (gets current). The laser emits a light beam that's split into two. One beam goes to a sensor that detects pulses of light. A circuit generates a steady clock signal. The system measures the difference between the clock signal and the laser pulse. A control circuit adjusts the negative voltage on the absorber based on a generated signal that's generated using the clock signal. During laser off-time, the control unit sends a fixed voltage; during laser on-time, it sends a voltage that changes at a set frequency. The control circuit also adjusts the current into the gain section based on the timing difference, changing the pulse strength.
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July 3, 2012
June 11, 2013
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